The present invention generally relates to solid phase immunoassay tests for providing sensitive detection of an analyte in a biological fluid sample and is more particularly directed to a colored contrast method therefore.
Lateral flow immunoassay tests in typical use today, generally include a porous component of nitrocellulose membrane, as the solid, with specific reagent applied onto specific zones therein.
An upstream zone usually includes a specific binding reagent for the analyte being tested, conjugated to a visible label such as a gold colloid or colored latex particle. The labeled reagent is formulated to facilitate its release from the membrane after the sample is applied to the test strip.
In typical competition assays, a sample containing analyte is introduced to a sample area of the test strip. Migration of the sample, caused by the capillary wicking within the porous membrane; re-suspends the labeled reagent from its stationary position on the strip. As the reagent mixture migrates along the strip it is brought into contact with the immobilized capture reagent. If the analyte is present in the sample, binding to the labeled reagent (antibody-visual label) will take place during this migration.
If the amount of analyte is enough to exhaust all binding sites on the labeled reagent, binding of the visual label to the capture reagent will not occur. This constitutes a positive result.
If there is no analyte in the sample, the visual label will bind at the capture zone producing a negative result seen as a colored band or site.
For the most part, these tests are interpreted visually by human eye to determine the presence or absence of an analyte (drug). Membranes like nitrocellulose provide a white background to visualize the presence or absence of the colored line or site. Presently, white is the only color commercially available for nitrocellulose membrane.
Partial sight, aging, and congenital color deficits can produce changes in perception that reduce the visual effectiveness or certain color combinations.
The present invention provides for a method for enhancing visual perception of a colored site in lateral flow immunoassay device utilizing complementary colors to provide better contrast for visual perception of test results.